This is a user-to-user help forum, so you are probably better off contact Chilkat directly by e-mail regarding licensing questions.

However, it looks like a 1 developer license to SFTP is $149, up to 4 developer license is $199, and an unlimited developer license $249. All of the above come with 1 year of support.

That said, I highly recommend buying the Chilkat bundle. For less than 2x the price of a single component license, you get access to the entire suite of libraries, and while you might not think that you need them now, I think you will find that they will be very useful in the future. In particular the HTTP, FTP, IMAP, Email, Crypto, and ZIP libraries are very handy.